1. Field of the Invention
The present invention relates to a differential device and a method of manufacturing the same, the differential device comprising: a differential mechanism; and a differential case housing the differential mechanism, the differential case including: first and second bearing bosses formed integrally therewith on one side portion and another side portion of the differential case and aligned on a same axis to be supported by a transmission case via bearings; an annular flange formed integrally with the differential case on an intermediate portion which is offset from a center of the differential case toward the second bearing boss side; work windows for inserting the differential mechanism, the work windows being provided in portions of a peripheral wall of the differential case which face each other on a diametral line orthogonal to the axis, the flange having a ring gear press-fitted to an outer peripheral surface thereof; and a press-fit portion between the flange and the ring gear being welded on the second bearing boss side.
2. Description of the Related Art
Such a differential device is known as disclosed in International Publication No. WO2013-18223.
In the differential device disclosed in International Publication No. WO2013-18223, wall thickness of a flange of a differential case is uniform over an entire periphery, and welding of a press-fit portion between the flange and a ring gear is performed on right and left opposite side portions. In a case where work windows are formed to be large in order to facilitate inner surface machining of the differential case and insertion of a differential mechanism into the differential case, the work windows may cut into a side surface of the flange on a first bearing boss side to form recessed portions. In a case of a differential case having such recessed portions, all-around welding of the flange with the ring gear on the opposite side portions causes various problems. For example, in a case where the side surface of the flange on the first bearing boss side is welded, a position of a welding torch needs to be changed in accordance with shapes of the recessed portions, and operation efficiency is decreased. Moreover, even if the work windows are covered with jigs to prevent spatters produced during the welding from entering the differential case, the spatters are prone to enter the differential case due to the existence of the recessed portions. Further, when a side surface of the flange on a second bearing boss side is welded as well, piercing welding is prone to occur in the recessed portions because the wall thickness of the flange is small in portions corresponding to the recessed portions. As a result, the spatters scatter toward the first bearing boss side, and may adhere to an inner surface of the differential case.